Today's portable communication systems set up communication among multiple portable communication devices and stationary base stations on a multitude of channels, where uplink transmissions are transmissions from the portable communication device to the base station and downlink transmissions are transmissions from the base station to the portable communication device. Some signaling protocols specify uplink transmissions on more than one channel, such as a control channel and a data channel. Thus, transmitter circuitry of a portable communication device can be transmitting on one or more adjacent channels, possibly leading to adjacent channel leakage. Accordingly, it is necessary to control the transmitter circuitry to avoid such issues.
In wide-band CDMA (WCDMA), the transmitter circuitry can be controlled to reduce adjacent channel leakage problems by performing rate selection which includes selecting the data rate and coding scheme (also known as Transport Format Combination (TFC) selection) for a signal transmission or burst to control the transmitter circuitry's power amplifier. In newer specifications for WCDMA, there are at least five channels that need to be supported for uplink transmission: a dedicated physical control channel (DPCCH), a dedicated physical data channel (DPDCH), a high speed dedicated physical control channel (HS-DPCCH), an enhanced dedicated physical control channel (E-DPCCH), and an enhanced dedicated physical data channel (EDPDCH). The rate selection for the enhanced uplink channels (E-DPCCH and EDPDCH) is referred to as enhanced transport format combination (E-TFC).
An appropriate E-TFC can be selected from the transmitter configuration characteristics of the transmitter circuitry by computing a maximum power reduction (MPR) for the waveform to be generated and the given transmitter configuration. Transmitter configurations can be characterized by one or more channels in the code, frequency, or time domain or any combination thereof and may include other attributes such as channel modulation type. For example, an uplink transmitter configuration for WCDMA may be characterized by two or more code channels with differing modulation, spreading factor, channelization code, and I or Q branch assignments. Thus, the number of transmitter configurations can be quite large, and each transmitter configuration has a corresponding MPR. In addition, over each transmission time interval (TTI) different transmitter configurations may be selected resulting in waveforms with different linear headroom requirements. Due to the large number of E-TFCs and transmission configurations, it is very complex for E-TFC selection to compute and store each E-TFC in real time. In addition, calculating all possible E-TFCs for all possible transmitter configurations off line and storing them in the portable communication device requires an enormous amount of memory.
Thus, what is needed is a method and apparatus for E-TFC selection which allows for power reduction on the uplink channel without being too complex for real time calculation or too memory intensive for storage of a table of all possible E-TFCs for all possible transmitter configurations. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.